1. Field of the Invention
The present invention generally relates to a manufacture method and structure of a curved capacitive touch panel, and more particularly to a method of molding a capacitive touch panel with curved shape, and a touch panel manufactured based on the method.
2. Description of the Related Art
Resistive and capacitive touch panels are two common types of touch panel technologies. The capacitive touch panel usually includes a touch panel circuit, which is manufactured by stacking a number of transparent conductive materials (such as indium tin oxide (ITO)) on a transparent substrate using a photolithography technique such as exposure, developing and etching, thereby resulting in a transparent capacitive touch panel. The touch panel circuit may alternatively include a flexible printed circuit board (FPCB), which is attached to the substrate, thereby resulting in an opaque capacitive touch panel. A touch on the touch panel results in a capacitance effect between the touch panel circuit and human body, and the touch position may then be accordingly detected.
As curved surfaces are the latest design trend of opto-electronic products, conventional physical keys or art lines thus cannot readily be in harmony with the curved surfaces of such designs and may add complexity in manufacture. The curved surfaces in the opto-electronic products are discussed, for example, in UK Patent No. 1110377, Japan Patent Publication No. 2002341323, China Patent Publication No. 1612185 and the curved liquid crystal display (LCD) announced by AU Optronics Corp. in June 2008. However, that literatures concerns the application of the curved surface in safety glass or LCD, rather than in touch panel devices.
For the foregoing, a curved touch panel is disclosed, for example, in U.S. Pat. No. 6,654,071, which discloses a flexible capacitive touch panel that is capable of being bent and thus conforming to the curved surface of a display, and is then attached to the display to form a display with touch sensing/detecting capability. China Patent Publication No. 1479891 provides a curved capacitive touch pad, which includes a film inserted between two transparent rigid curved plates. The touch panel in U.S. Pat. No. 6,654,071 and the touch pad in China Patent Publication No. 1479891, however, are bent along only one axial direction, such as the vertical axis or the horizontal axis of the touch panel. Moreover, no manufacturing details have been disclosed in the publications.
In order to overcome these problems, US Patent Publication No. 20080042997 discloses a curved resistive touch panel, which is manufactured by firstly attaching a flat polarization plate to a touch panel, and then pressing the composite polarization plate/touch panel into a curved shape. According to this manufacture method, the polarization plate and the touch panel may end up being discarded as wasted material whenever the pressing step fails. Further, the portion with lower stress intensity in the composite polarization plate/touch panel may fracture partially or result in interference fringes during the pressing step.
Furthermore, due to better transmittance and resistance to scratch, wear and deform, glass is preferably used as the composing material for the substrate rather than plastic (e.g., polyethylene terephthalate or PET). High temperature (e.g. 650-750° C.) is required to bend the glass substrate to form a curved glass substrate. However, the FPCB may crack at 300° C. Therefore, the FPCB and the flat glass substrate unfortunately cannot be made curved at the same time.